Dorsal spinal column stabilization by means of a screws/rod system involves inserting the fixation rod as gently as possible into the tulip of pre-set adjacent pedicle screws. A variety of approaches for the design of such rod insertion instruments are known.
In the case of the rod insertion instrument according to EP 2 353 530 A1, a gripping head for the fixation rod sits over a pin on a central inner shaft of the instrument, on which a displaceable sleeve is guided, with which displaceable sleeve a pivoting of the gripping head about 90° via a handle arrangement is possible. In order to introduce the fixation rod, this is initially brought into a position in which it is oriented essentially parallel to the inner shaft. Subsequently the gripping head is pivoted about approximately 90° by actuation of the sleeve by using the handle arrangement, whereupon the fixation rod is navigated into the tulips of the pedicle screws.
The stability of this known rod insertion instrument is relatively limited due to the transmission configuration required for this system.
In order to provide more stable connections to the fixation rod, it is known to directly pivotably fix the fixation rod onto the rod insertion instrument. These solutions are shown for example from documents EP 2 305 154 A1, WO 2007/025132 A2 or US 2011/0313475 A1. The problem of these known rod insertion instruments however lies in the fact that the orientation of the fixation rod during insertion is often not sufficiently exactly controllable.
Finally a rod insertion instrument has become known from document WO 2011/143550 A1, whereby the fixation rod is adjustable and is fixable at the distal end of the rod insertion instrument. However this arrangement requires a relatively complex design of the proximal end of the fixation rod and of the corresponding complementary surfaces on the rod insertion instrument.
A generic rod insertion instrument is distributed by the Applicant AESCULAP AG under the product code FW 240 R. With this rod insertion instrument the insertion of the fixation rod takes place with a fixed angular position assignment between fixation rod and tube section. In this way, it is possible to introduce the fixation rod with good control and also minimally invasively or percutaneously into the body. In order to provide a good angular position for rod insertion, the gripping head is marginally angled with respect to the tube section within the order of magnitude of approximately 30° such that the fixation rod accommodated in the gripping head, during insertion into the tulips of the adjacent pedicle screws, includes an obtuse angle with the axis of the tube section of approximately 120°. While this fixedly set angular position between rod insertion instrument and fixation rod is also advantageous for the handling of the instrument, this design however also brings with it the problem that during screwing in of the so-called ‘set screws’ into the pedicle screws for fixing the fixation rod, over-stressing of the soft tissue in the region of the adjacent skin incision can often occur.